There is a need for highly potent TB treatments that can cure disease in substantially fewer than the six months currently required. Rifapentine is a long-acting rifamycin that has potent anti-TB activity and is currently FDA-approved for TB treatment at a dose of 600 mg twice weekly. Evidence using a mouse model of TB treatment indicates that a multi-drug regimen containing daily rifapentine can cure TB within three to four months. However, there are critical knowledge gaps;the efficacy of daily rifapentine has not been assessed in clinical trials and the optimal dose of once daily rifapentine for clinical use is not known. Preclinical and Phase 1 studies suggest that the optimal daily dose is likely to lie between 450 and 600 mg. The overall goal of this proposal is to determine the optimal daily dose of rifapentine in the context of multidrug intensive phase treatment for pulmonary TB, in order to guide dose selection for future Phase 3 clinical trials. The proposed Phase 2 clinical trial is intended to determine the antimicrobial activity and safety of rifapentine doses of 450 mg and 600 mg administered once daily with isoniazid, pyrazinamide, and ethambutol during intensive phase (first eight weeks) treatment of smear-positive pulmonary TB in Cape Town, South Africa.